The present invention relates to a web slitter for cutting an endless web.
A web-slitting machine or system typically employs a number of web-slitting assemblies to cut an endless moving web, such as a continuous roll of paper or other material, into a number of strips (equal to the number of web-slitting assemblies plus one). The web-slitting machine supports and permits the positional adjustment of the web-slitting assemblies, thereby permitting the machine to be configured to cut any one out of a wide variety of strip width sets.
Referring to FIGS. 1 and 2, a prior art web-slitting assembly 10 includes a web slitter 12 that overlaps with a lower knife 22, so that together they present a scissors-like action to a continuous web of material which is pulled through the assembly 10 by a drum or a take-up reel (not shown). The web slitter 12 includes an upper carriage 16, which is slideably movable along a support in the form of a transverse bar 14, and a blade holder 18 that includes a freely rotating disk-shaped blade 20. The lower knife 22, which may be in the form of a drum or roller that has a sharpened edge, is positioned on a supporting sleeve 24.
Referring to FIG. 2, the upper carriage 16 of web slitter 12 includes a brake shoe 26, which engages a dovetail-shaped projection 15 of the transverse bar 14. The brake shoe 26 may be operated pneumatically or by turning rotary brake knob 28. The transverse position of the carriage assembly 16 along the transverse bar 14 is adjusted by turning transverse control knob 30, which is connected to a shaft 32 (FIG. 2) which terminates in a pinion gear 34.
The upper carriage 16 is connected to the blade holder 18 by a dovetail-shaped guide key 38, which is selectively removable from the upper carriage 16. An added feature of this construction is that the blade holder assembly 18 may be reversed relative to the upper carriage 16 by merely sliding the blade holder assembly 18 off of the guide key 38, rotating it 180xc2x0, and sliding it back on, thus permitting either a right-hand or left-hand orientation.
A rotary control knob 52 provides mode control for the pneumatic systems, which power the locking of the upper carriage 16 to the transverse bar 14, the lowering of the blade holder assembly 18 toward the knife 22, and the shifting of the rotary blade 20 laterally toward the knife 22. More specifically, the control knob 52 permits an operator to command standby, setup or run mode. In standby mode, blade holder 18 is held at a raised and disengaged position. To function properly during run mode, the blade 20 and knife 22 must press against each other with a force that is within a proper range. If the force is too light or nonexistent, the web may not be slit. If the force is too great, the blade 20 may break. Accordingly, in run mode, blade holder 18 is not only lowered, but also moved to the side by a side-shift cylinder (not shown) having a maximum cylinder stroke distance. If carriage 16 has been correctly positioned on bar 14, this will cause blade 20 to contact and press against the knife 22 with an acceptable force. In setup mode, blade holder 18 is lowered and shifted to the side by the side-shift cylinder, thereby permitting an operator to move the web slitter 12 along the transverse bar 14 and to thereby place and press the blade 20 against the knife 22. By locking the carriage 16 in place at the resultant position the operator has readied web-slitting assembly 10 for run mode operation. However, the operator must exercise judgment and skill for the blade to press with an acceptable force against the knife 22 during run mode.
U.S. Pat. No. 5,058,475, referenced and incorporated above, simplifies the task of the operator by providing a xe2x80x9chalf-strokexe2x80x9d button. This button, when depressed, causes the side-shift cylinder to be stopped half-way through its stroke. During setup mode, an operator can depress the half-stroke button and move the web slitter 12 laterally along the transverse bar 14 so that the blade 20 contacts the lower knife and locks the carriage in place at the resultant location. After this, during run mode, the blade 20 will contact the knife 22 half-way through the stroke of the side-shift cylinder, with the remaining pneumatic pressure introduced into the side-shift cylinder pressing the blade against the knife 22. This xe2x80x9chalf-strokexe2x80x9d amount of force is approximately the optimum amount of force for the blade 20 to press against the knife 22. This innovation provided a definite advantage over the prior art of the time. Unfortunately, in practice it has been found that operators sometimes forgot to depress the xe2x80x9chalf-strokexe2x80x9d button during setup mode, thereby completely nullifying the affect of this button.
It is important in the design of web slitting machines that the shear or cant angle between the blade 20 and lower knife 22 be set precisely. The cant angle is the angular relationship between the blade 20 and the lower knife 22 in the plane of the blade 20 about a vertical axis. This angle must be set accurately so that the wear and deformation between the two cutting edges are kept to a minimum.
The need for accuracy in the setting of the cant angle complicates the performance of the following described reconfiguration of a web-slitting assembly. A blade 20 that is positioned to cut against a first edge of a knife 22 at a first cant angle will eventually wear away the first edge. It is then desirable to switch the relative positions of the blade 20 and the knife 22 so that the blade 20 makes contact with the knife""s second edge, which is unworn. As shown in FIG. 1, the blades 20 are asymmetrically shaped to have a knife-contacting-side and a side that never contacts a knife 22. As a result, when it is desired to shift the blade arrangement so that the blade 20 contacts the knife 22 at the knife""s second edge, it is necessary to reorient the blade 20 by about 180xc2x0. As noted earlier, a simple 180xc2x0 rotation can be effected simply by sliding the blade holder 18 off of the guide key 38, rotating it 180xc2x0, and sliding it back on.
Unfortunately, the cant angle of the blade 20 also must be shifted to a mirror image angle of the first cant angle relative to a plane parallel with the faces of knife 22. Heretofore, there appears to have been no method for quickly and easily effecting this shifting of the cant angle, forcing the operator to make a time-consuming manual cant angle adjustment.
Another problem is encountered in that different makes of web-slitting machines have differently shaped bars (such as bar 14) for supporting web slitters. Heretofore, as a result, a web slitter had to be manufactured specifically to be accommodated by the bar shape of a particular make of web-slitting machine.
In addition, a problem is encountered in a system such as that of FIGS. 1 and 2 in which a removable blade holder 18 is supported by a piston that is housed in a cylinder (not shown) in the carriage 16 and that is driven down to engage the blade 20 with the knife 22 and driven up to disengage blade 20. If the blade holder 18 also includes one or more pneumatic actuators, the task of supplying these actuators with pneumatic pressure in the carriage 16 has typically been performed by a set of external hoses (not shown), each linking a source of pneumatic pressure to a receive port in the blade holder 18. The advantage of this arrangement is that the hoses circumvent the piston and accommodate the various distances between the carriage pneumatic pressure sources and the blade holder 18. A disadvantage of this arrangement, however, is that every time the blade holder 18 is replaced or reoriented, the hoses must be disconnected and reconnected. An additional disadvantage is that the hoses are exposed and therefore vulnerable to damage by operating personnel.
Yet another problem is encountered in a system, such as the one described above, in which a piston (not shown) moves the blade holder 18 up and down. When the piston is moved up, it creates a momentary drop in air pressure in the lower portion of its host cylinder. This drop in air pressure tends to draw the lint-filled air of the blade-slitting environment into the lower portion of the cylinder, thereby degrading system performance over time.
The present invention is an improvement of the web slitter shown in the aforementioned U.S. Pat. No. 5,058,475 incorporated herein.
In one preferred aspect of the web slitter, a carriage and a blade holder are releasably and matingly interconnected by a connective assembly enabling selective reversal of the blade holder between opposing orientations about a vertical axis. A blade cant angle adjustment assembly enables a choice of either a first predetermined blade cant angle or a second predetermined blade cant angle, each adapted for a respective different one of the opposing blade holder orientations.
In another separate preferred aspect, a blade positioning assembly, in response to user selection of a setup mode, automatically moves the blade over only a predetermined partial portion of its maximum horizontal travel distance.
In another separate preferred aspect, the web slitter assembly is adapted to be fastened selectively to respective first and second web slitter tracks of different configurations.
In another separate preferred aspect, a first fluid passageway is located on one side of a piston which provides vertical adjustment of the blade. An enclosed second fluid passageway circumvents the piston to communicate between the first passageway and an actuator which moves in unison with the piston on the opposite side thereof.